1. Field of the Invention
The present invention relates to an attachment apparatus for use in a crane or other cargo handling equipment.
2. Description of the Prior Art
In a cargo handling operation, a crane or a fork lift truck is generally employed in accordance with a particular situation. To unload articles placed on a rack or a similar structure, a crane is not generally used alone, and it is common to equip a crane with a fork-type attachment. In this case, however, it is necessary to align the center of gravity of an article with the center of suspension and to employ a special arrangement for the rack or shelf, which fact involves an extremely low operating efficiency. A conventional attachment apparatus is, as shown is FIGS. 36A and 36B, arranged such that the position of suspension is changed in accordance with the weight of each of the articles A. With such an attachment apparatus, although it is convenient to lift up the article A when it is placed on the floor, it is impossible to unload the article A when it is placed on a shelf. In the latter case, it is accordingly necessary to design a slide-type shelf on which it is possible for the article A to be easily pulled out to the front side of the shelf where the article A can be lifted up by the attachment apparatus.
In the case where certain articles are handled, for example, when an article of continuous length is to be unloaded from a shelf, it is inconveniently necessary to employ two or more attachment apparatuses in order to handle the article in a well-balanced state. Moreover, when an article to be handled has an excessively large size or weight, it is not possible for the conventional attachment apparatus to align the center of gravity of an article with the center of suspension in order to obtain a well-balanced condition of the article.
Further, employment of an overhead travelling crane involves an unfavorably low operating efficiency and certain risks in a goods handling operation, since the crane is incomplete in terms of the control of its brake system, that is, it is not possible for the crane to stop immediately in response to a power supply cut-off of the driving means, and the crane undesirably moves a certain distance before coming to a stop.
On the other hand, when a fork lift truck is employed, a space is needed to allow the fork lift truck to move freely. An article of continuous length requires a particularly large space. Thus, cargo handling operations involve various kinds of restrictions.